Testicular cancer is mostly diagnosed by a painless induration or enlargement of the affected testis. Primary evaluation comprises clinical examination as well as high-resolution scrotal ultrasound, including the contralateral testis. The diagnosis can be confirmed by elevated serum tumor markers α-fetoprotein or β-hCG. The definitive diagnosis is made by an inguinal exploration of the affected testis. Contralateral bifocal biopsy should be considered in the presence of risk factors for a contralateral germ cell neoplasia in situ (GCNIS). Computed tomography of chest/abdomen/pelvis is the standard staging procedure of testicular cancer patients at primary diagnosis. MR tomography of abdomen/pelvis instead of CT scans is a viable option in the follow-up of testicular cancer patients to reduce radiation exposure. Histogenetically, testicular tumors are classified into germ cell tumors, stromal tumors, or mixed forms. Among germ cell tumors, seminomas are the most common isolated tumor type (60%). The most common stromal tumors are Leydig and Sertoli cell tumors, which are mostly nonmalignant. Testicular germ cell tumors (TGCTs) are classified by their local growth and the presence or absence of regional/distant metastasis according to the UICC-TNM classification. The IGCCCG prognostic classification is mandatory for metastatic TGCTs, as it determines further treatment decisions.